Difficult to say really as the second car, a mighty Yaris, only covered a few thousand miles a year and we only had it three years.
When we got it, the Yaris, had brands of tyre I'd never heard of so swapping those for new Michelins was not a good basis for comparison.
When we did get rid of the car the tyre tread did look new though.
They wore well on the front of my mk5 though, I probably did 20k in them before I drove down the worlds biggest pothole and damaged the sidewall of one, so both fronts got replaced for PS4. I only did this as I'd noted it was hardly below 7 degrees for the two winters I ran them so decided against getting another pair of cross climates.
My understanding from reading up on proper winter tyres is that the tyre compound is much softer which means they work really well in the cold but wear quickly when it's not cold or cold. The cross climates have lots of extra sipes/slits in the tread to help with grip in the cold, rather than a much software compound than summer tyres.